Currently, a tooth is prepared for a crown in the following manner. First, during an initial office visit, the dentist makes an impression of the portion of the mouth in which the tooth is located, with upper and lower occlusal surfaces. From this impression a lab technician will later create a stone study model.
The dentist then removes tooth material with a high-speed drill, relying on eyesight and expertise to create a form on which a crown will be cemented. This form begins with a narrow shoulder at the gum line and tapers inward as it rises to a flattened top that ends just below the lowest level of the tooth's original biting surface.
The dentist then makes an impression of the prepared tooth and sends it to the lab technician along with the original tooth impression, prepared prior to removal of tooth material. The dentist makes and installs a temporary crown for the prepared tooth.
Using the impression of the prepared tooth, the lab technician produces a crown that matches the dentist's color and material specifications and sends it to the dentist. At the patient's second visit, the dentist tests and adjusts the crown as necessary before cementing it in place.